Utility and industrial plants are subject to increasingly strict limits with respect to air emissions and waste water discharge. Compliance with government regulations add significantly to the capital and operating costs of utility and industrial plants powered by fossil fuels. Traditionally, compliance with air emission limits was achieved through the use of wet flue gas desulfurization (WFGD) or dry flue gas desulfurization (DFGD) systems. The capital cost of such systems and the associated Balance of Plant (BOP) systems add significantly to the overall cost of power generation. BOP systems include for example associated ductwork, fans, bulk material handling systems, and like associated plant equipment and systems. BOP systems typically costs 200 to 500 US Dollars/kilowatt ($/kW). In retrofit situations, the capital cost associated with environmental compliance may render a plant uneconomical. In addition to capital investment, WFGD and DFGD systems also involve substantial operating costs associated with reagent consumption, auxiliary power usage, operation staffing and maintenance staffing.
Compliance with current waste water discharge limits are achieved in a variety of ways, which may be as simple as combination/dilution of multiple plant waste water streams into a single compliant stream, or as complicated as waste water treatment systems involving neutralization, precipitation of heavy metals, biological treatment, filtration, and/or similar such treatment steps. Examples of flue gas cleaning systems and/or waste water treatment systems can be appreciated from International Publication No. WO 2006030398, U.S. Patent Application Publication Nos. 2009/0294377, 2011/0262331, 2012/0240761, 2013/0248121, and 2013/0220792, U.S. Pat. Nos. 6,076,369, 7,524,470, 7,625,537, 8,388,917, and 8,475,750, European Patent Publication No. EP 1 955 755, and Japanese Published Patent Application No. JP 2012200721.
With increasingly strict limits being established with regard to air emissions and waste water discharge, efficient and economical systems and methods for reducing gas emissions from WFGD waste water streams are needed.